There is an increasing call for population-wide environmental/policy interventions to improve dietary and physical activity patterns. This proposed longitudinal study will link contemporaneous geographic locations of respondents with diet-related (e.g., food shopping and eating options) and activity-related (e.g., recreation, community design) built environment variables to data from an exceptional dataset including quality diet and physical activity data. We focus on the young and middle adult periods which appear to be important in the etiology of adult obesity. We examine adult weight change during the period of stabilization into the work force followed into mid-adulthood with the Coronary Artery Risk Development in Young Adults Study [CARDIA] >5,000 young adults. We focus on shifts between the early adult period of ages 18-30 years and 20-year changes up to ages 38-50. A critical component is to see how these environmental factors relate to health disparities. We will use complex longitudinal and spatial analytical models to explore relationships between the built environment and dietary intake patterns. One element addressed will be residential self-selection, an issue of increasing concern as scholars attempt to understand how the environment affects health behaviors. We will examine race/ethnic differentials in these effects and the impact of the built environment shifts over time and through the lifecycle. We will also study how these dietary and activity behaviors, in turn, affect weight dynamics and incident obesity and also examine direct relationships between the built environment and the etiology of weight gain and incident obesity. The focus will be on examining how modifiable built environmental factors will affect the key proximate determinants of obesity (diet and activity) and in turn affect weight dynamics and obesity. A central issue is determining modifiable environment factors that may reduce ethnic and socioeconomic differentials in health status.